The role of male pheromones of a moth Y' padellus in sexual behaviour'

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The role of male pheromones of a moth (Y.
padellus) in sexual behaviour.
Aletta C. Bakker, Peter Roessingh and Steph B. J.
Menken UvA, IBED, Kruislaan 320, 1098 SM
Amsterdam, The Netherlands, abakker_at_science.uva.nl
Introduction Little is known about the function
of pheromones of male moths. Male pheromones are
generally believed to function as aphrodisiacs
that play a role during courtship behaviour.
However actual evidence for their mode of action
is scarce. In some cases, males form a lek and
use pheromones to attract females over long
distances. Male pheromones can serve as a signal
for both sexes.
We believe that male pheromones are potentially
important signals for assortative mating and
sexual selection. In this poster we present
methods and results on the study of sexual
behaviour, female choice and the function of the
male pheromone of a moth Yponomeuta padellus.

Evidence for pheromone production in Yponomeuta
males. Many male moths have structures called
hairpencils. It is believed that the large
surface of such structures facilitate the
diffusion of volatiles like male pheromones.
Analysis through SEM and videotape observations
of Yponomeuta padellus males supported the
presence and use of these hairpencils during
sexual behaviour. Yponomeuta males also exhibit
wingfanning behaviour which could further
facilitate pheromone dispersal.
Photo from video of male that fully protruded his
two hairpencils (arrow).
SEM photo of abdomen tip of male with hairpencil
(6) extended.

Attraction of males to female pheromone and
females to male pheromone in a y-tube. We used an
y-tube olfactometer to study the response of
females to the male pheromone. First we performed
a control experiment to confirm male attraction
to female pheromones in our set-up. We observed a
significant response of males towards synthetic
female pheromone when clean air was the
alternative (n20 p0.012 Binomial Test).
Subsequently we tested female response to the
odours of male moths exposed to synthetic female
pheromone when the single synthetic pheromone was
the alternative. We found no significant effect
(n 32 pgt0.05 Binomial Test). A control
experiment showed no effects of the synthetic
female pheromone on the behaviour or choice of
females. Preliminary conclusion females do not
show a preference for male pheromone in a simple
y-tube test.
Assortative mating or not? In experiment 1
females from two host plants (Prunus and
Crataegus) were offered a choice between two
males (brothers) raised on either of these two
host plant. Females preferentially mated with
the male from the same host plant (assortative
mating). In experiment 2 we used non related
males (as what would be expected in the field).
This showed however no such preference of the
females. The experiments should be repeated using
moths from one population and identical set-up
conditions before we can draw any
conclusions.

What we want to do next Sperm transfer is sperm
transfer the same for the first, second, third
etc. mating of the male? Female choice do
females prefer a virgin male over a male that has
already mated? Do females prefer an unrelated
male over a related male? Sexual behaviour
Analyses of importance of wingfanning and
behavioural patterns for mating success (Theme,
Noldus B.V.). Chemical compounds of the male
pheromone Testing new methods for non-invasive
sampling (solid phase micro extraction) and using
GC-MS for identification of male pheromone
compounds.
Male investment sperm transfer. There is a
significant difference in weight change between
the mated (n13) and unmated (n11) individuals
plt0.001. The Pearsons correlation between weight
change of females and males is 0.72 (p0.003).
Our results show that males loose 13.5
(S.E.0.5) of their body weight when they mate
compared to 2.3 (S.E.0.2) natural weight loss
when they do not mate. Conclusion Males do
invest! It has to be tested what the composition
of the spermatophore is in apyrene and eupyrene
sperm and whether a nuptial gift is involved.
Acknowledgments Louis Lie (culture of
Yponomeuta), Maarten Hilbrant (SEM, photo
hairpencils) Jacco Jong (y-tube experiments) and
Marieke de Boer Paulien de Bruijn (assortative
mating experiment 1).